RCA桃園廠地下水污染物分布與演變

Distribution and Evolution of Groundwater Contamination at the RCA Taoyuan Plant

饒以馨(I-Hsin Yao)

指導教授 ： 賈儀平

國立臺灣大學/理學院/地質科學研究所/碩士(2015年)

https://doi.org/10.6342/NTU.2015.01022

摘要

RCA(Radio Corporation of America)桃園廠於1987年發現廠區土壤和地下水受含氯有機化合物污染，污染源可能來自於廢液滲漏或傾倒。主要污染物為四氯乙烯、三氯乙烯、1,1,1-三氯乙烷等含氯有機化合物及其降解產物，為重質非水相液體(Dense Non-Aqueous Phase Liquid, or DNAPL)。在地下水中溶解度極低，難以使用抽除或處理的方式完全清除。此場址已發現污染約二十餘年，本研究將整理此場址之歷史資料，並且評估整治措施之成效及後續待加強之工作。
桃園廠區歷經多次現地調查與採樣分析，淺處為約20公尺厚的礫石含水層，深處則為砂泥互層組成的含水層。當地的水力梯度指出，溶解於地下水中的污染物在水平方向是往北傳輸，而垂直方向則是往深處流動。污染物多分布於廠區西北與北側，1998年曾挖除污染的土壤加以曝氣及現地抽氣方式清除土污染，並採用抽水與處理方式進行先導性地下水污染整治，但未實質改善。後續試驗現地化學氧化整治法亦未成功，2005年起在廠區使用加強式還原脫氯法進行現地生物整治，將糖蜜和生物營養製劑注入地下水，加速含氯有機化合物脫氯降解作用。七年後地下水中四氯乙烯及三氯乙烯污染濃度多已大幅降低至管制標準以下，然而經生物降解後產生的氯乙烯難以繼續降解，部分監測井的氯乙烯污染濃度仍超過管制標準，而且毒性更強。此外多年來污染物已擴展至廠外鄰近地區，未來亟需思考如何清除地下水中的氯乙烯，並整治廠外的地下水污染。

關鍵字

RCA桃園廠 ； 地下水 ； 污染整治 ； 四氯乙烯 ； 三氯乙烯 ； 氯乙烯

並列摘要

Soil and groundwater at the Radio Corporation of America (RCA) Taoyuan Plant in Taiwan were found contaminated by chlorinated volatile organic compounds (VOCs) in 1987. The pollution may be attributed to improper dumping or leakage of chlorinated solvents. The major pollutants are tetrachloroethylene (PCE), trichloroethylene (TCE), 1, 1, 1- trichloroethane (1, 1, 1-TCA) and their degradation byproducts. These VOCs are dense non-aqueous phase liquids (DNAPLs) which can hardly be dissolved in groundwater. The residual DNAPLs along the migration pathway usually dissolve very slowly in groundwater, and thus become long-term contamination sources.
Site characterization indicated that the uppermost aquifer is a thick gravel layer. The deep aquifer is composed of sand interbedded with mud layers. Groundwater flows northward horizontally and downward vertically. Contamination was found primarily in the northwest and north sides of the plant. The pump and treat method had been implemented, but failed to remediate groundwater contamination. Enhanced reductive dechlorination method has been adopted to clean up contaminants since 2005. By injecting reducing agents, the aquifer condition became favorable to anaerobic biodegradation. The concentration of PCE and TCE in the groundwater reduced significantly at most wells seven years later. However, the concentration of vinyl chloride (VC), a highly toxic chemical produced through biodegradation processes, exceeded the regulatory standard at many wells. Besides, the contaminants have migrated off-site for years. Therefore, an effective solution for the cleanup of VC contamination and off-site contamination should be considered in the future.

並列關鍵字

RCA Taoyuan Plant ； groundwater ； contamination remediation ； tetrachloroethylene ； trichloroethylene ； vinyl chloride

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